As the evolution of batteries continues, and particular as lithium batteries become more widely accepted for a variety of uses, the need for a safe, long-lasting, high energy battery becomes more important. Various exotic chemistries are available which are capable of producing high-voltage and large quantities of current. Nevertheless, while electrochemistries exist which are capable of producing desired results, if these systems are incapable of being economically and effectively packaged to permit long-term shelf life, and continued operation over the theoretical life of the system, they are of little value. Laboratory curiosities have little utility until they are developed and engineered to the point where a safe and effective product can be manufactured for sale.
One particular problem lies in the area of battery terminals, which are absolutely essential if these exotic chemistries are to be able to discharge the much desired quantities of energy and power. As with higher energy systems, the very nature of the high electrochemical potential presents problems with side reactions, corrosion and incompatibility of materials. In particular materials such as sulfur dioxide which are employed as depolarizers are found to be highly corrosive, vigorously attacking most metals which are employed at the terminal pin. By far the most effective material for use as a terminal pin in these types of batteries is aluminum. Aluminum very fortunately has the desirable property of being compatible with lithium sulfur dioxide chemistries so that an aluminum terminal pin will not corrode or be otherwise adversely affected by the system. However, aluminum is not without other properties which cause difficulties in the manufacture of an acceptable commercial product. Sulfur dioxide systems are, by their nature, pressurized, which require an effective and complete seal of the terminal pin as it passes from the inside of the cell to the exterior. By far the most effective type of seal would be a glass to metal seal which would be hermetic and protect the user from noxious sulfur dioxide. Aluminum, unfortunately, is incapable of withstanding the temperatures necessary for the formation of a glass to metal seal.
Accordingly, it is an object of this invention to provide a seal for a battery terminal pin which employs an aluminum metal or metal alloy thereof in a manner which prevents escape of the sulfure dioxide. A further object of this invention is to provide a seal means for a lithium-sulfur dioxide battery which does not employ high temperatures, thereby permitting the use of aluminum terminal pin. Other objects will appear hereinafter.